Analytical instruments which rely upon regulated fluid flow are commonly employed in a wide variety of applications, such as sample purification, chemical analysis, clinical assay, and industrial processing. For many instruments, an extensive and complex array of tubing, fittings and connectors are employed to provide the many flow paths that are necessary for optimum operation, and to effect the attachment of sensors, valves, and the like.
Such instruments typically function with use of devices that initiate, maintain, halt, or reverse a flow stream through the device. This may be accomplished by combinations of valves and/or pumps. Very often, such instruments devices require a complex arrangement of multiple flow paths to operate efficiently. Generally, efficient operation requires a flow system combining flow-through components, such as sorbent columns and connective tubing, with terminal components, such as needles, pumps, and drains. Different flow paths are frequently required to, for example, isolate a component from the flow system, include a component into the flow system, or rearrange the order of the components in the flow system. Further, there is the need to sense certain characteristics of the fluid flow at differing points in the flow paths. Examples of such sensed characteristics include the pressure, flow rate, and temperature of the fluid. Other characteristics related to the particular fluid flow include the presence or absence of a fluid component, such as an analyte or contaminant. Such needs are typically addressed by the use of fluid connectors for attachment of differing, plural sensors.
Combinations of fluid connectors are typically necessary to provide flow paths among the flow-through components and terminal components employed in a flow system.
There exists the practical problem, therefore, of connecting the valves, sensors, fittings, and the like that are required for the multitude of flow path combinations in a modern analytical instrument. Hence, another practical problem remains in connecting quite a large number of devices in a multitude of flow path combinations in an instrument. The complexity of such systems introduces reliability concerns. Because the devices that are implemented in these flow systems are sometimes automated, the reliability and accessibility of the pneumatic connection are features critical to successful instrument operation.
Another problem involves the proper orientation of all of the valves, sensors, and the like so as to allow the desired combinations of flow paths, yet also provide an assembly that is compact, easily-manufactured, inexpensive, and reliable. For example, the provision of fluid-tight connections in a complex fluid-handling assembly has become exceedingly problematic as the assembly is reduced in size.
Gas and liquid chromatographs are particular examples of an instrument having a fluid flow system wherein certain characteristics related to a particular fluid flow are detected, e.g., the presence or absence of a fluid component, such as an analyte or contaminant. Some gas chromatographs employ fluids in the form of combustible gasses in performing an analysis. Even though the pneumatic fittings in the typical chromatograph are designed to minimize leakage, one may nonetheless consider a pneumatic fault mode wherein a gas leak could occur and sufficient gas could accumulate so as to pose an unsafe condition.
The instrument may also require a complex array of fluid connections that are specialized (non-standard or require expensive or low volume parts) such that their manufacture is labor- and capital-extensive.
It will also be appreciated that a flow system in an instrument must be versatile, that is, capable of being configured during assembly, or reconfigured to meet the requirements of a particular application as additional valves, fittings, etc. are added to the flow system.
In response to these problems, U.S. Pat. No. 5,567,868, issued to Craig et al., disclosed an analytical instrument, preferably in the form of a chromatograph, that includes a computer, a pneumatic controller responsive to the computer, and planar manifold assembly. The planar manifold assembly includes one or more fluid-handling functional devices attached to a planar manifold. Multiple fluid-handling functional devices may then be coordinated and assembled so as to connect to pneumatic channels that are integrated in the planar manifold, and thus many of the fluid flow paths are integral to the planar manifold, which is itself quite compact and amenable to construction in a variety of shapes and configurations. The advantages of the planar manifold assembly include the reduction of external connections between fluid-handling functional devices (such as fittings, valves, sensors, and the like) by use of a single planar manifold for the provision of a plurality of flow paths. The fluid-handling functional devices that connect to the planar manifold are constructed to be surface-mounted to offer reliable, fluid-tight connection without the complexity and difficulty of previously-known pneumatic connections.
Nonetheless, there still remains a difficulty in effecting such fluid connections between one or more channels in the planar manifold and a corresponding channel or conduit in one of the great variety of differing devices, tubes, fittings, and the like that are attractive for use with the planar manifold assembly. A significant disadvantage of presently known connectors is that they have a dead space communicating with the ends of the fluid channels being coupled. A portion of the fluid emerging from the end of one channel quickly finds its way into the dead space but a relatively long time is required for it to enter the other channel. For example, in a tube connected by conventional means to a detector in a chromatograph, the concentration of a sample fluid emerging from one end of the tube can increase rapidly to a maximum value and then slowly decay to zero so as to cause a phenomenon known as tailing. As those skilled in the art are aware, this can make it difficult to detect separate components of the sample.
Another significant disadvantage of presently known fluid connector devices is that the fluid flowing through a fluid connector device can be degraded by contact with large areas of less-than-inert surfaces of the device.
Another significant disadvantage of presently known fluid connector devices is that many fluid handling devices, and the planar assembly itself, are becoming even smaller and are designed to be assembled in a compact, densely-populated arrangement. Conventional fluid connectors, in contrast, remain undesirably large and bulky.
There is accordingly a need in many applications for a fluid connector system for use in effecting a pneumatic connection to a channel in a planar manifold assembly or similar planar device in an analytical instrument, wherein such a system would offer such attributes as: miniaturization, reliability, simplicity, robust, ease in assembly and maintenance, and low cost.